Surface coatings can used to impart articles with desirable properties that are not possessed by the articles themselves or not possessed in a sufficient degree. For example, there are myriad applications for which it would be desirable to use electrically conductive and/or thermally conductive components having good physical properties. Because of their intrinsic conductivities and frequently advantageous physical properties, metals are often useful for such applications but can have drawbacks, including increased weight, cost, and that they can be difficult and/or inconvenient to form into a variety of shapes, including intricate parts.
Many of these drawbacks can be overcome by the use of polymeric materials, which can have cost, weight, processability, and flexibility of design advantages over metals. However, most polymer materials are not intrinsically electrically or thermally conductive enough for many applications. Conductive polymeric resin compositions can be made in some cases by adding fillers to polymers, but high loadings are often required, which can be to the detriment of physical and other properties of the materials, as well as lead to melt processing difficulties when thermoplastic materials are used, among other possible drawbacks.
In many cases, it would be sufficient for only a portion of a part be conductive. For example, as electronics become more and more pervasive, it is becoming increasingly important that a variety materials having electromagnetic interference (EMI) shielding properties be readily available. Housings for many electronic parts can be conveniently made from polymeric materials, but few useful polymers are sufficiently
electrically conductive to be EMI shielding, necessitating the use of conductive additives, which can often have deleterious effects on other properties (such as physical properties) of the materials. It would thus be desirable to conveniently obtain an electrically conductive coating that could be applied to a polymeric housing or other article to achieve a desired degree of EMI shielding.
Electrically conductive coatings can also be advantageously used with metals. For example, electrically conductive coatings can be used to provide metal structures with long-lasting corrosion resistance.
Coatings can also be used for countless other applications, including providing UV radiation resistance, abrasion resistance, thermal conductivity, impact resistance, stiffness, and many others.
It would be desirable to obtain coatings that can be used with a wide variety of substrates to provide useful properties.
U.S. Pat. No. 6,265,466 discloses an electromagnetic shielding composite having nanotubes. U.S. Pat. No. 7,060,241 discloses electrically conductive films including carbon nanotubes. U.S. Pat. No. 7,118,693 discloses conformal coatings that provide shielding against electromagnetic interference that comprise an insulating layer and a conducting layer containing electrically conductive material. US 2007/0092432 discloses thermally exfoliated graphite oxide.